Photographic image transfer process



Aug. 21, 1956 E. H. LAND PHOTOGRAPHIC IMAGE TRANSFER PROCESS 2 Sheets-Sheet 1 Original Filed Feb. 12, 1948 Phoiosensifive Shed Mcd'eriul Viscous Processing Ageni FIG.

Layer of Processing Ageni' Confainer for R O T N E V N Processing Ageni' Aug. 21, 1956 E. H. LAND PHOTOGRAPHIC IMAGE TRANSFER PROCESS 2 Sheets-Sheet 2 Original Filed Feb. 12, 1948 Suppor'l' Phoi'o. Emulsion Processing Agen'l Non-adhering film Silver Precipi'l'ql'ing Sl'rai'urn FIG. 6

Base

United States Patent PHOTOGRAPHIC' IMAGE TRANSFER PROCESS Edwin H. Land, Cambridge, Mass, assignor to Polaroid Corporation, Cambridge, Mass, a corporation of Delaware Original application February 12, 1948, Serial No. 7,795. Divided and this application February 9, 1951, Serial N 0. 210,125

11 Claims. (Cl. 95-88) This invention relates to photographic processes and more particularly to transfer processes wherein a latent image in a silver halide emulsion is developed and wherein components are transferred from said emulsion to a print-receiving element to form a positive print in the latter.

This application is a division of my copending application Serial No. 7795, filed February 12, 1948, for One- Step Photographic Transfer Process (now Patent No. 2,647,056, issued July 28, 1953).

One object of the present invention is to provide a novel transfer process in which the processing liquid is spread in a thin layer over the surface of a print-receiving eiement and a photosensitive element, and the printreceiving element is provided with a surface from which the viscous film of processing agent may be readily stripped.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following. detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

Figure 1 is an enlarged fragmentary and diagrammatic view in perspective illustrating one stage in the process of the present invention;

Fig. 2 is a view similar to Fig. 1 illustrating another step in the process;

Fi g. 3 is a view similar to Fig. l in which there is illustrated an alternative method for introducing the liquid processing agent between the two sheet materials;

Fig. 4 is a fragmentary enlarged perspective view illustrating the construction of the container of Fig. 3, the thicknesses of the laminations of the sheet materials from which the container is formed being greatly exaggerated;

Fig. 5 is a perspective view of the filled and sealed container; and

Fig. 6 is a diagrammatic enlarged sectional view illustrating one embodiment of the product of the present invention shown in use in the performance of a transfer process.

The present invention is particularly useful in processes wherein a photosensitive, silver halide emulsion layer or the like containing a latent image has a positive of the subject matter of said latent image formed upon a separate print-receiving element. In the performance of such processes, the processing agent, when spread in a layer, develops a latent image in the area of the photosensitive layer over which it is spread and the development of this latent image produces an imagewise distribution throughout the photosensitive layer and/or the liquid processing layer adjacent thereto of a material which thereafter acts to provide the positive print in the print-receiving element, the latter being superposed upon the photosensitive layer during this processing with the layer of processing agent located between it and the photosensitive layer.

In one form of this type of processing, there is pr vided in the spread liquid composition a developing agent for the latent image and a material capable of forming a soluble complex with the photosensitive material of the emulsion. The complex-forming material and the developing agent react with the photosensitive layer in such a manner that the latent image is developed and a soluble complex is formed with the relatively unexposed, undeveloped photosensitive material of the emulsion. This complex is transported from the photosensitive layer and the silver thereof is caused to precipitate and aggregate in a print-receiving element to form a positive image.

In other processes which may be carried out in accordance with the invention, the imagewise distribution of the developer or the oxidation product of the developer resulting from the development of the latent image in the photosensitive layer is used to create a visible image in the print-receiving element. In one such process, the imagewise distribution of the unused developing agent acts to form a substance which produces the visible image. In another modification, the oxidized developer is employed to react with a substance in a surface stratum of the print-receiving element to form, for example, a dye image. This dye image is a negative of the subject matter of the latent image in the event the photosensitive emulsion is the ordinary non-solarized emulsion, and is a positive of the subject matter of the latent image in the event the emulsion is of the type which gives direct positives upon exposure and development, e. g., emulsions which have been optically or chemically solarized or which use other reversal effects such as the Herschel effect.

In general, therefore, the print-receiving elements of the present invention are particularly useful in the performance of transfer processes wherein the layer of liquid composition which is located between the sheet material comprising the photosensitive layer and the print-receiving element acts to develop a latent image in said photosensitive layer, and such development produces an imagewise distribution of a material which is capable of providing said print-receiving element with a visible positive or negative image record of the latent image. The inclusion of the film-forming material in the liquid composition in connection with these transfer processes serves further functions. It provides a spacer for the two sheet materials which tends to hold the same far enough apart so that there is a reservoir therebetween for the ions and molecules that must enter and leave the sheet materials during the processing while keeping the surfaces of said sheet materials near enough together so that the imageforming particles which are translated from the photosensitive layer are made up of components which have arrived along a relatively short radius of diffusion. The presence of the film-forming material in the liquid processing agent also serves to cause the latter to temporarily bond together the two sheet materials tightly enough to prevent such separation or relative movement thereof as might tend to diffuse the image being formed by the transfer process.

In accordance with the present invention, the printreceiving element is so constituted that when the same is stripped from the photosensitive element the film formed by the processing agent adheres to the photosensitive element so that a minimum of the reaction products of the processing which produces the positive print in the printreceiving element remains upon said print-receiving element, thereby tending to greatly improve the stability of the print.

Referring to the drawings, and particularly to Figs. 1 and 2, there is illustrated one manner of performnig the process of the present invention' A photosensitive sheet material of which a predetermined area 12 is to be processed has a portion thereof, in advance of said area, located between a pair of pressure-applying members such as a pair of pressure rollers 14-14 and a printreceiving element 16 is introduced between said pressureapplying members so that a portion thereof is superposed with respect to the portion of said photosensitive material located between said members. There is introduced into the troughlike cavity formed adjacent the pressure-applying members by sheet materials 10 and 16 a mass 18 of the viscous film-forming processing agent in a quantity at least sufficient to carry out the processing of said area, said mass of processing agent being preferably distributed throughout a length parallel to and coextensive with the linear dimension of said area which it adjoins. Thereafter, the sheet materials are moved in superposed relation between said pressure rollers so that the latter progressively apply a compressive force to successive increment areas of said sheet materials, spreading said processing agent 18 in a thin layer 20, as shown in Fig. 2.

The separation of the pressure rollers and the thicknesses of the sheet materials predetermine the maximum thickness of the layer of the liquid processing agent that is obtained between said sheet materials. Said sheet materials may be moved with respect to said pressure rollers by being pulled therethrough manually, or by rotating the rollers to cause the frictional engagement between said rollers and said sheet materials to advance the latter therebetween, or by fixing the edges of said sheet materials extending through said rollers with a suitable clamp and then moving the rollers with respect to the sheet materials.

Other types of pressure-applying members such, for example, as a pair of nonrotatable bars or a pair of plates or a pair of jaw-shaped members or a plate and a roller may be employed instead of the pressure rollers to effect the spreading.

The processing agent may be dispensed between the sheet materials from a suitable container as, for example, a tubular, collapsible, metallic container of the type used for containing tooth paste, shaving cream, and the like. It will be observed (Fig. 1) that the liquid is located, upon dispensation, in a fairly concentrated mass 18 having a relatively small exposed surface area and that the relatively thin layer 20 of large surface area which is thereafter obtained by the spreading of the agent (Fig. 2) is protected on both sides thereof by the two sheet materials between which it is spread, thus minimizing the effects of oxidation.

The liquid composition may also be provided in a condition to be dispensed and spread between said sheet materials 10 and 16 by being contained in an elongated container 22 which has a length at least equal to a transverse linear dimension of the area 12 of photosensitive material 10 to be processed. Container 22 is located between the two sheet materials adjacent and substantially parallel to an edge of said area which parallels said linear dimension.

Container 22, which may be attached to one of sheet materials 10 and 16, is preferably inexpensive and disposable and so constructed as to be capable of retaining the processing composition therein for relatively long periods of time without vapor loss or oxidation. One example of a suitable container of this type is formed from a single multilayer sheet of material 30 (Fig. 4) comprising three layers, 30a, 30b and 300. Layer 30a, which provides the internal surface layer of the container, is formed of a material which is chemically inert to the processing agent and which is impervious to the liquid of the agent. One class of materials suitable for: this purpose, particularly where the processing agent is an alkaline solution of a developer for silver halide or the like, is the polyvinyl acetals, and of the acetals polyvinyl butyral is a preferred species. A composition comprising to 72% by weight of polyvinyl butyral, 10% to 23% by weight of nitrocellulose, and approximately 5% by weight of dibutyl sebacate is particularly satisfactory as inner coating 30a. Layer 15% contiguous to layer 30a is preferably impervious to the vapor of the processing agent and is formed, for example, of a metallic foil such as lead or silver foil. Backing layer 300, for example of kraft paper, is provided and makes possible the use of thinner layers 30a and 30b.

The container 22 (Fig. 5) is preferably formed by taking the single sheet of material 30 and folding the same medially, as shown in Fig. 4, and thereafter securing the end marginal portions 32 and the longitudinal portions 34 of the two folded faces to one another, providing a central space or cavity for containing the processing agent. To fill the container, it is possible to adhere together the opposite longitudinally extending marginal portions 34 and the end marginal portions 32 at one end only of the container, the container being filled through the other end, which is thereafter sealed.

The longitudinal seal between marginal portions 34 is preferably such that upon application of a predetermined compressive force to the walls of the container there may be created within the container a sufficient hydraulic pressure to separate the marginal portions 34 throughout substantially their entire length. To insure this, the bond securing together said marginal portions 34 is somewhat weaker than the bond which secures together end marginal portions 32. For example, the end portions may be secured by pressing the two polyvinyl butyral inner surfaces together and applying heat thereto while a sealing strip 36 may be provided between the longitudinal marginal portions, which sealing strip is adapted to adhere to the inner layers of polyvinyl butyral with a lesser affinity than said layers adhere to one another in a direct polyvinyl butyral to polyvinyl butyral bond. Strip 36 may be formed of a material such as ethyl cellulose or a mixture of ethyl cellulose and paraffin.

For carrying out the process a preferred form of the processing agent comprises a water solution of a developer, an alkali for imparting to the solution a sufficiently high alkalinity to permit the developer to carry out its developing function, a substance for forming a soluble complex with silver halide, and a film-forming material. When this agent is spread between a photosensitive silver halide emulsion and a print-receiving element, the developer in the agent acts to develop any latent image in the emulsion and the silver halide solvent forms a soluble complex with the relatively unexposed silver halide during the development, which complex is transported from the emulsion to the print-receiving element to form in said element a positive image comprising silver of the developed image in the emulsion. The film-forming material, which is preferably a high molecular weight polymer, imparts to the composition a predetermined high viscosity and is of such character as to retain its viscosity-imparting and film-forming properties in an aqueous alkaline solution so that the processing agent, once its ingredients have been mixed and have attained an equilibrium, remains uniformly viscous for any given temperature for long periods of time.

The film-forming material in the foregoing alkaline composition is preferably one of the class of high molecular weight polymers which include in their chemical structure such groups as, for example, the ether, alkyl, hydroxyl, carboxyl and acetyl groups that are stable to alkalis and which contain none of the chemical groups, such as the ester and acid chloride groups, that are unstable to alkalis. The polymers also contain groups such as the hydroxyl and/or carboxyl groups which tend to solubilize in aqueous alkaline solutions. Suitable examplesqof :such'; polymers are; .theealkali-inere -andy,.water,-.

soluble; cellulose: derivatives. suchv, 38 sodium carbox-y methyl cellulosenand;.hydroxyethyl cellulose, andathe; alkali inert and water-soluble l-polyalkane derivatives such as-polyvinyl alcohol;v and c1116 sodium salts .of ?polymethacrylic acid and polyacrylio acid.

A high viscosity for the processing agent isivery desirable since it makes possible the relatively uniform spreading of the composition and in'suresa complete coverage of thedesired area .bysaid composition. The,.,film-fo rming material is preferably containedinthe composition in suit-.

hydroquinone, b'romohydroquinone, toluhydroquinone,.

xylohydroquinone, o-aminophenol, 2-amino-5-diethylaminotoluene hydrochloride, p-tertiary butyl catechol, hydroquinone disulfonic acid "(potassium salt), 2,5-ditertiary butyl hydroquinone, and p aminodie'thylanaline.

Examples of materials whichmay be used in the com-- position for the purpose of forming asoluble silver complex with the undeveloped silver halide of the, photosensitive layer are sodium thiosulfate, sodium thiocyanate, ammonium 'thiosulfate, ammonia and sodium cyanide. Whena compound is toxic, suchas sodium cyanide, precautions should be'taken in theuse thereof;

Thecomposition may also contain sodiumsulfite' which acts in part as a preservative; and may also function as a silver halide solvent.

Examples of processes forforming a positive imageof a latent image contained-in a-silver halide emulsion by means of the transformation ofundeveloped silver halide to a soluble complex anda'the-translation thereof to a suitable image-receiving layer are given below, but it isto be expressly understood that these examples are merely illustrative and" that the --invention is not limited to the" materials orproportions set out therein.

Example 1 A processing agent is prepared which comprises: Water grarns 1860' 1 Sodium carboxymethyl cellulose do 117 Sodium sulfite do- 78 Sodium hydroxide do 74.6 Sodium thiosulfate do 14.5 Citric, acid do 38.5 Hydroquinone do 52 The processing agent is prepared by dissolvingthe sodium carboxymethyl cellulose, for example the commercially available Hercules 1362 medium viscosity type, in the water in a -mixer at roomtemperature, andithe solution is mixed therein .fon approximately one 1 hour.

Thereafter, the sodium. sulfite, sodium hydroxide, sodium;- thiosulfate .andcitric acidareadded. to.the.-solution',-the.

addition being effected in,an.iner,t atmosphere, for example of nitrogen. Upon dissolution of these materials, the hydroquinoneis add'ed'and the solution 18 further mixed for an hour at approximatelyroom temperature in a nonoxidizing atmosphere of nitrogen.

Theprocessing .agent 'isuthen -spread,-. for example, as; sh'oWninFigs. ,1 and 2,, betw.eerr a;,ph0tosensrtrve:sheet.- 111311611811 1 and the. novel: printrrece ving element .16;:to.

forma laminate comprising sheet 10, f a layer -20-ofthe. processing agent, and element 16 (Fig. 6). Sheet-10 may comprise a support 10a of paper or transparent film base such as a cellulosic ester or a cellulose mixed ester and a photosensitive silver halide emulsion 10!) such as an orthochrornatic, high contrast emulsion especially useful for process work, for example, the emulsion ofEastman Kodak Contrast Process Ortho film, or an emulsion of an enlarging paper such as the emulsion of Eastman Kodak Kodabromideipaper. This emulsion constitutes theinner. surface of sheet 10.: The layer of processing agent 20 is preferably spreadbetween said sheet materials to a thick-- ness of between .002 inch and .003 inch. The absorption oftheliquid by emulsion 10band the surface. portion of element 16 promptly reduces this layer to a thickness ofthe order of .0001 inch to .0003 inch. Layer 20 bonds together sheet materials 10 and 16 :just tightly enough so that they donot separate spontaneously during the time.

of processing. The lamination-thus. formed is kept intact for approximately one to two minutes,- and at the end of this time element 16'is strippedfrom sheet 10, leaving a finished positive image on ele'ment16.

Base .or support 16a of element 16 ispreferably baryta paper although it may-be formed ofsuch other materials as, for example,, regeneratedv cellulose, a polyhydroxyalkane such as polyvinyl alcohol, sodium alginate, cellulose ethers such as ethyl cellulose,.ortheir derivatives such as sodium carboxymethyl cellulose, aluminum carboxymethyl cellulose and hydroxyethyl cellulose, other papers, proteins such'as gelatin andcarbohydrates such as gums. andstarch, and mixtures of these-materials-Where the latter are-compatible.

Faster emulsions such, for example, as the emulsions available. foruse in amateur'photographyas negative materials may also be used. Examples of the faster emulsions are the relatively high-speed.orthochromatic films, e.. g., Eastman Kodak-Verichrornefilm having an ASAspeed rating .of 0200 and an ASA exposure index rating in the daylight of 50, and the extremely high speed panchromatic Example-1 issubstantially increased, being preferably 1 quadrupled. Improvements in the photographic characteristics, of the positive image may also be .obtained by suitably applying to the print-receiving element substances for attracting and aggregating the, image-forming ions. amples of such substances aremthe metallic sulfides such, for example, as lead sulfide, cadmium sulfide, zinc sulfide, ferric sulfide, antimony-sulfide, manganous sulfide, titanium sulfide sodium sulfide, lanthanum sulfide, palladium sulfide, nickelous sufide, and such metallic selenides aszinc selenide, nickel selenide, lead selenide, manganous selenide and antimony selenide, and such other substances as dithiooxamide and its lead and zinc complexes, potassium dithiooxalate and the lead complexes thereof, and thioacetamide.

These precipitating. materials are preferably appliedto the surface of the base 16ain mixtures of a suitable, rela-- tively inert material ,such'assilica'aerogel (Santocel'C), wood flour, clays, for example kieselguhr and bentonite, starches, ground glass, and celites.- An example of suitable compositions for treating a base 16a of baryta paper to form-thereon a silver precipitating layer l6b' is-the following:

Example 2 Baryta paperis run through a bath which is kept in contactwith the baryta surface for approximately ten seconds,

the bath comprising:

The sheet thus obtained is dried and coated with a mixture comprising:

Water cc 270 Cadmium acetate eg 27.8 Lead acetate g 9.3 Zinc nitrate g 55.6 Silica aerogel (Santocel C) g 30 3% solution of sodium sulfide cc 94.7

The sheet is preferably dipped into this mixture and the excess mixture is removed from the sheet as, for example, by the action of a soft buffer roll on said sheet as it leaves the bath.

To cause the film-forming material of layer 20 to adhere to photosensitive sheet material instead of printreceiving element 16 so that the solid plastic film obtained from said film-forming material sticks to the photosensitive material 10 when the latter is stripped from element 16, there is provided over stratum 31617 a layer 16c. Layer 16c is preferably very thin and is formed of a material which has an appreciably lesser affinity for the filmforming material of layer than said filrn-forming material has for the surface of sheet material 10 which it contacts. In the event emulsion 10b is a silver halide gelatin emulsion and the film-forming material in layer 20 is sodium carboxymethyl cellulose, layer 160 may be, for example, gum arabic, cellulose acetate-hydrogen phthalate, polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, cellulose nitrate, sodium alignate, pectin, and polymethacrylic acid. Layer 160 preferably has a thickness of the order of 1 to 3 microns, although if it is relatively water permeable its thickness may be appreciably greater.

The adhesion between the carboxymethyl cellulose in layer 20 and the surface of layer 10b may also be increased by applying to said surface or by incorporating adjacent said surface in said emulsion a substance which tends to insolubilize sodium carboxymethyl cellulose by causing cross-linking of the molecules of the latter, examples of such substances being lead acetate and zinc acetate. The photosensitive emulsion may be treated with these materials by being dipped in a solution thereof. The afiinity between emulsion 10b and the film-forming material of layer 20 may also be appreciably increased by applying to the surface of said emulsion a thin coating of solid film formed of said film-forming substance.

To provide a sheet 16 with a stratum 16b containing precipitation nuclei, a sheet of baryta paper may have the baryta surface thereof coated as described in Example 2, or it may be processed as follows:

Example 3 A sheet of baryta paper has roll coated thereon a thin layer of a composition comprising:

% solution of polyvinyl alcohol cc 110 1% solution of sodium sulfide cc 48 1% solution of neutral lead acetate cc 76 Either of the sheets processed in accordance with Exampics 2 and 3 and thereby provided with an image-receiving stratum 165 may be suitably processed to be provided with a stripping overcoat 160, for example in the following manner:

Example 4 The processed sheet has roll coated thereon against a smooth surface such, for example, as the polished surface of a metal drum, a 5% aqueous solution of polyvinyl alcohol in a layer whose thickness is of the order of .001 inch. An equivalent amount by weight of hydroxyethyl cellulose or polymethacrylic acid may be substituted for the polyvinyl alcohol of this example.

Example 5 The processed sheet is dipped into a 2% solution of cellulose acetate, the cellulose acetate being dissolved in 8. a mixture of methanol, ethyl acetate and methyl cellosolve, the proportions of said solvents being in the ratio of 1:3 :3 by volume, respectively. The dipped baryta paper is removed from the solution in a vertical position to permit the excess liquid to drip ofi, a sufiicient quantity of the solution remaining on the surface of the paper to provide the latter with a coating of cellulose acetate of the desired thickness.

Example 6 A 10% solution of cellulose acetate-hydrogen phthalate in acetone is roll coated on the processed sheet in a thickness of approximately .001 inch.

In a similar manner, such other materials as methyl cellulose, cellulose nitrate, sodium alginate, ethyl cellulose and gum arabic and pectin may be applied as layer 16c to the processed sheet. It is, of course, understood that suitable solvents for the materials are employed, said solvents being preferably water for such materials as are readily water soluble, and may be toluene for ethyl cellulose and a mixture of methanol and ethyl acetate for cellulose nitrate.

In using the sheets processed in accordance with any of the foregoing examples, the adhesion between the filmforming material and the photosensitive emulsion may be increased by applying to the photosensitive emulsion a thin coating of the film-forming material. For example, when the film-forming material in the processing agent is sodium carboxymethyl cellulose the surface of layer 1012 may be treated as follows:

Example 7 A 5% water solution of sodium carboxymethyl cellulose is applied to layer 10b in a darkroom as, for example, by being spread thereon by a doctor blade to a thickness of approximately .002 inch. This film, when dried, will give a very thin layer of sodium carboxymethyl cellulose and will improve the adhesion between the layer 10b and the solid film formed from the processing agent.

It may be desirable in some instances to provide on the surfaces of sheet 16 a single layer which combines the properties of layer 160 and stratum 1611, i. e., a single layer which serves to lessen the affinity between sheet material 16 and the film-forming material, and is so constituted as to attract the soluble silver halide complex and to precipitate the silver therefrom. Such a layer may be provided on base 16a, for example as follows:

Example 8 A solution consisting of:

To cc. of the resulting mixture there is added 20 cc. of a solution of gum arabic such as Arabol. The mixture thus obtained is rubbed on a sheet as, for example, by a bufiing roll in a thin layer onto a sheet of baryta paper which has been previously dipped for approximately ten seconds in a solution comprising:

Cadmium acetate g" 9 Neutral lead acetate g .3

Zinc nitrate g 18 Water cc 100 Example 9 A sheet of baryta paper has roll coated thereon in a layer of a thickness approximating .002 inch a composition comprising:

8% solution of polyvinyl alcohol cc 220 4% solution of sodium sulfide cc 12 12% solution of neutral lead acetate cc 6 Eaiample'aIO A sheet of baryta paper has roll coated thereon-.in a layer of a-thicknessapproximating ,002'inch a composi tion comprising;

50% solution of egg albumen acc 100'- 40% solution neutral lead acetates. cc 48 1% solution sodium sulfide cc .t 15

15 solution ascorbic acid cc ,t 9

Example 11 A sheet of baryta paper: has -rollwcoatedthereon in a layer of a thickness approximating -;;002' inch-a composition comprising;

50% solution of 'egg albumen; cc 100" 50% solution of gelatin; cc 5 48% solution of neutral lead acetate cc 48 1% solution sodium sulfide.- cc' 15 15% solution ascorbic. acid; cc 9 In another form of the invention, a dye-image; is

formedin a lstratum of -a sheetmaterial 16w The' following is an example of 'sucha process:

Example 12 A viscous film-forming compositionwisuprepared .by mixing together the. following materials:

5% water solution of sodium" carboxymethyl cel=' lulose g. 60. Pyrocatechin g 2 sodiumhydroxide; g 1.5. 2% water solution-of. Calcocid blu e-AX 200 (C.

tion of cellulose acetate in a mixture of methanol, ethyl,

acetate and methyl cello'solve, the proportions-of the three solvents being in the ratio of 1:323 lby ,volume, respectively. The thin film is obtainedbyrdippingthe baryta paper into this solution andthenremoving the same in a vertical position to permit the excess solution to drip off,-a sufficient quantity ,of' the solution remainington the surface of the paper to give a film of desired thickness to provide said baryta paper with'a coatingof cellulose acetate of the desired thicknessa Theliquid processing agent isspread between the coated side of' element 16 and the emulsion side of photosensitivelayer 10 and the developer develops the latentzimagein'the photosensitive layer and tans the gelatin in the neighborhood of the developedportions thereof. The dye in the liquid processing agent is taken up bythesc .tannedlporticns, producing an imagewise disposition of dye in the liquid composition. This dye penetrates th'roughl the coating of cellulose acetate to provide a stratum of element 16-with a positive-dye image, The separation of sheet materials 10 and 16 causes the filmr-forming materialtoftheliquid composition toaadhere to the surface of photosensitive sheet material. 10.

Since certain changes-maybe made in the above process without departing from the scope oflthe invention herein involved, it is intended that all matter "contained said .layert'to. a tprecipitatingglayer"ioii a lprint-receivingi'i element; which process comprises the :steps of spreading between the said silver halide layer of said photosensitive element and a surface of said print-receiving elementa viscous processing composition which comprises as a component thereof. a film-forming thickening agent capableof giving a continuous solid film when the composition is dried after spreading,the stratum of said print-treceivingaelement contiguous to said surface thereof being permeable to the liquidof said processing com v position and comprising a plurality of layers, the outermost of said layersbeing a strippingtlayer which provides' said spreading .surface vand permits the print-receiving element to be stripped from the solid thicken- .ing agent ofsaid processing composition subsequent to the formation of the transferaprint on said-print-receiving element, said stripping layer comprising as its principal constituent at least one high molecular weight film-.- forming polymer from the class consisting of gum arabic,

cellulose acetate-hydrogen phthalate, polyvinyl alcohol,

hydroxyethyl cellulose,"methyl cellulose, ethyl cellulose, cellulose nitrate, sodium alginate, pectin and polymethacrylic acid, another layer of said stratum beneath said stripping layer being a precipitating layer, the latter comprising particles of silica among which is dispersed a reagent capable of coacting with the processing composition to cause said transfer print to be formed in said precipitating layer, said stripping layer being substantially free'of said-silica and of said reagent, the liquid of said processingicomposition, upon permeation of said silver halide layer, containing reagents, including a silver halide developer, for'developing the latent image in said silver halide -layenand for forming transferable components for transfer to said precipitating layer, transferring said components to said precipitating layerto form therein a visible image 'ofsaid latent image,'and separating said print-receiving element from said photosensitive element, the stripping layer of said print-receiving element causing the residue of said processing composition to strip along with said photosensitive element.

2 The process of claim 1 wherein the film-forming thickening agent is a high molecular Weight polymer from'the class consisting of the alkali-inert, water-soluble cellulose and polyalkane derivatives.

3.The process of claim 1 wherein thefilm-forming thickening agent is sodium carboxymethyl cellulose.

4. A-method of producing visible images of a latent image contained in a silver halide layer of a photosensitive"element by the transfer of components fronrsaidlayer to a precipitating layer of a print-receiving elementgwhich process comprises the steps of spreading between thesaid silver halide layer of said photosensitive element and a surface of said print-receiving element a viscous processing composition which comprises as a component thereof a film-forming thickening agent-capable of giving a continuous solid film when the composition is dried after spreading, the stratum of said printreceiving element-contiguous tosaid surface thereof be ing permeable to the liquid of said processing compo-sh tion and comprising-as its outer surface stratum, a stripping layer which provides said spreading surface and which-permits the print-receiving element to be strippedfrom the solid, film-forming thickening agent of said? processing composition subsequent to the forrnationo-f: the transfer print on said print-receiving clement, said stripping layer'cornprising polyrnethacrylic acid as a principal ingredient' thereof,'said permeable stratum also including a precipitating layer beneath said stripping layer, saidprecipitating-layer comprising particles of a waterinsoluble, inorganic substance and a reagent capable of coacting with the processing composition to cause said transfer print. to be formed in said precipitating layer, said stripping layer being substantially free of said particles of inorganic substance and oft-saidtreagent, the liquid of said processing composition, upon permeation of said.

silver halide layer, containing reagents, including a silver halide developer, for developing the latent image in said silver halide layer and for forming transferable components for transfer to said precipitating layer, transferring said components to said precipitating layer to form therein a visible image of said latent image, and separating said print-receiving element from said photosensitive element, the stripping layer of said print-receiving element causing the residue of said processing composition to strip along with said photosensitive element.

5. The process of claim 4 wherein the film-forming thickening agent is a high molecular weight polymer from the class consisting of the alkali-inert, water-soluble cellulose and polyalkane derivatives.

6. A method of producing visible images of a latent image contained in a silver halide layer of a photosensitive element by the transfer of components from said layer to a precipitating layer of a print-receiving element, which process comprises the steps of spreading between the said silver halide layer of said photosensitive element and a surface of said print-receiving element a viscous processing composition which comprises as a component thereof a film-forming thickening agent capable of giving a continuous solid film when the composition is dried after spreading, the stratum of said print-receiving ele ment contiguous to said surface thereof being permeable to the liquid of said processing composition and comprising, as its outer surface layer, a stripping layer which provides said spreading surface and which permits the print-receiving element to be stripped from the solid, film-forming thickening agent of said processing composition subsequent to the formation of the transfer print on said print-receiving element, said stripping layer comprising gum arabic as a principal ingredient thereof, said permeable stratum also including a precipitating layer beneath said stripping layer, said precipitating layer comprising particles of a water-insoluble, inorganic substance and a reagent capable of coacting with the processing composition to cause said transfer print to be formed in said precipitating layer, said stripping layer being substantially free of said particles of inorganic substance and of said reagent, the liquid of said processing composition, upon permeation of said silver halide layer, containing reagents, including a silver halide developer, for developing the latent image in said silver halide layer and for forming transferable components for transfer to said precipitating layer, transferring said components to said precipitating layer to form therein a visible image of said latent image, and separating said print-receiving element from said photosensitive element, the stripping layer of said print-receiving element causing the residue of said processing composition to strip along with said photosensitive element.

7. The process of claim 6 wherein the film-forming thickening agent is a high molecular weight polymer from the class consisting of the alkali-inert, water-soluble cellulose and polyalkane derivatives.

8. A method of producing visible images of a latent image contained in a silver halide layer of a photosensitive element by the transfer of components from said layer to a precipitating layer of a print-receiving element, which process comprises the steps of spreading between the said silver halide layer of said photosensitive element and a surface of said print-receiving element a viscous processing composition which comprises as a component thereof a film-forming thickening agent capable of giving a continuous solid film when the composition is dried after spreading, the stratum of said print-receiving element contiguous to said surface thereof being permeable to the liquid of said processing composition and comprising, as its outer surface layer, a stripping layer which provides said spreading surface and which permits the print-receiving element to be stripped from the solid, film-forming thickening agent of said processing composition subsequent to the formation of the transfer print on said printreceiving element, said stripping layer comprising cellulose acetate-hydrogen phthalate as a principal ingredient thereof, said permeable stratum also including a precipitating layer beneath said stripping layer, said precipitating layer comprising particles of a water-insoluble, inorganic substance and a reagent capable of coacting with the processing composition to cause said transfer print to be formed in said precipitating layer, said stripping layer being substantially free of said particles of inorganic substance and of said reagent, the liquid of said processing composition, upon permeation of said silver halide layer, containing reagents, including a silver halide developer, for developing the latent image in said silver halide layer and for forming transferable components for transfer to said precipitating layer, transferring said components to said precipitating layer to form therein a visible image of said latent image, and separating said print-receiving element from said photosensitive element, the stripping layer of said print-receiving element causing the residue of said processing composition to strip along with said photosensitive element.

9. The process of claim 8 wherein the film-forming thickening agent is a high molecular weight polymer from the class consisting of the alkali-inert, water-soluble cellulose and polyalkane derivatives.

10. A method of producing visible images of a latent image contained in a silver halide layer of a photosensitive element by the transfer of components from said layer to a precipitating layer of a print-receiving element, which process comprises the steps of spreading between the said silver halide layer of said photosensitive element and a surface of said print-receiving element a viscous processing composition which comprises as a component thereof a film-forming thickening agent capable of giving a continuous solid film when the composition is dried after spreading, the stratum of said print-receiving element contiguous to said surface thereof being permeable to the liquid of said processing composition and comprising, as its outer surface layer, a stripping layer which provides said spreading surface and which permits the printreceiving element to be stripped from the solid, filmforming thickening agent of said processing composition subsequent to the formation of the transfer print on said print-receiving element, said stripping layer comprising hydroxyethyl cellulose as a principal ingredient thereof, said permeable stratum also including a precipitating layer beneath said stripping layer, said precipitating layer comprising particles of a water-insoluble, inorganic substance and a reagent capable of coacting with the processing composition to cause said transfer print to be formed in said precipitating layer, said stripping layer being substantially free of said particles of inorganic substance and of said reagent, the liquid of said processing composition, upon permeation of said silver halide layer, containing reagents, including a silver halide developer, for developing the latent image in said silver halide layer and for forming transferable components for transfer to said precipitating layer, transferring said components to said precipitating layer to form therein a visible image of said latent image, and separating said print-receiving element from said photosensitive element, the stripping layer of said print-receiving element causing the residue of said processing composition to strip along with said photosensitive element.

11. The process of claim 10 wherein the film-forming thickening agent is a high molecular weight polymer from the class consisting of the alkali-inert, water-soluble cellulose and polyalkane derivatives.

Peters May 2, 1944 Rott June 20, 1944 (Other references on following page) UNITED STATES PATENTS Mullen Ian. 15, 1945 Murray Oct. 2, 1945 Land Feb. 27, 1951 McGraw et a1 Ian. 27, 1953 Land Dec. 28, 1954 FOREIGN PATENTS Great Britain Aug. 24, 1939 14 France Mar. 23, 1942 France Dec. 10, 1942 France (Addition) Jan. 22, 1945 Belgium July 31, 1941 Belgium Apr. 30, 1942 OTHER REFERENCES Rott: Sci. et Ind. Photo, 2nd Series, vol. 13, July- August 1942, pp. 151-152. 

1. A METHOD OF PRODUCING VISIBLE IMAGES OF A LATENT IMAGE COMTAINED IN A SILVER HALIDE LAYER OF A PHOTOSENSITIVE ELEMENT BY THE TRANSFER OF COMPONENTS FROM SAID LAYER TO A PRECIPITATING LAYER OF A PRINT-RECEIVING ELEMENT, WHICH PROCESS COMPRISES THE STEPS OF SPREADING BETWEEN THE SAID SILVER HALIDE LAYER OF SAID PHOTOSENSITIVE ELEMENT AND A SURFACE OF SAID PRINT-RECEIVING ELEMENT A VISCOUS PROCESSING COMPOSITION WHICH COMPRISES AS A COMPONENT THEREOF A FILM-FORMING THICKENING AGENT CAPABLE OF GIVING A CONTINUOUS SOLID FILM WHEN THE COMPOSITION IS DRIED AFTER SPREADING, THE STRATUM OF SAID PRINT-RECEIVING ELEMENT CONTIGUOUS TO SAID SURFACE THEREOF BEING PERMEABLE TO THE LIQUID OF SAID PROCESSING COMPOSITION AND COMPRISING A PLURALITY OF ALYERS, THE OUTERMOST OF SAID LAYERS BEING A STRIPPING LAYER WHICH PROVIDES SAID SPREADING SURFACE AND PERMITS THE PRINT-RECEIVING ELEMENT TO BE STRIPPED FROM THE SOLID THICKENING AGENT OF SAID PROCESSING COMPOSITION SUBSEQUENT TO THE FORMATION OF THE TRANSFER PRINT ON SAID PRINT-RECEIVING ELEMENT, SAID STRIPPING LAYER COMPRISING AS ITS PRINCIPAL CONSTITUENT AT LEAST ONE HIGH MOLECULAR WIEGHT FILMFORMING POLYMER FROM THE CLASS CONSISTING OF GUM ARABIC, CELLULOSE ACETATE-HYDROGEN PHTHALATE, POLYVINYL ALCOHOL, HYDROXYETHYL CELLULOSE, METHYL CELLULOSE, ETHYL CELLULOSE, CELLULOSE NITRATE, SODIUM ALGINATE, PECTIN AND POLYMETHACRYLIC ACID, ANOTHER LAYER OF SAID STRATUM BENEATH SAID STRIPPING LAYER BEING A PRECIPITATING LAYER, THE LATTER COMPRISING PARTICLES OF SILICA AMONG WHICH IS DISPERSED A REAGENT CAPABLE OF COACTING WITH THE PROCESSING COMPOSITION TO CAUSE SAID TRANSFER PRINT TO BE FOMED IN SAID PRECIPITATING LAYER, SAID STRIPPING LAYER BEING SUBSTANTIALLY FREE OF SAID SILICA AND OF SAID REAGANT, THE LIQUID OF SAID PROCESSING COMPOSITION, UPON PERMEATION OF SAID SILVER HALIDE LAYER, CONTAINING REAGENTS, INCLUDING A SILVER HALIDE DEVELOPER, FOR DEVELOPING THE LATENT IMAGE IN SAID SILVER HALIDE LAYER AND FOR FORMING TRANSFERABLE COMPONENTS FOR TRANSFER TO SAID PRECIPITATING LAYER, TRANSFERRING SAID COMPONENTS TO SAID PRECIPITATING LAYER TO FORM THEREIN A VISIBLE IMAGE OF SAID LATENT IMAGE, AND SEPARATING SAID PRINT-RECEIVING ELEMENT FROM SAID PHOTOSENSITIVE ELEMENT THE STRIPPING LAYER OF SAID PRINT-RECEIVING ELEMENT CAUSING THE RESIDUE OF SAID PROCESSING COMPOSITION TO STRIP ALONG WITH SAID PHOTOSENSITIVE ELEMENT. 